This proposal focuses on studying the molecular mechanisms of nuclear insulin signaling. Insulin-responsive trans-acting nuclear proteins binding to the human growth hormone promoter will be sought in insulin treated cells utilizing a mobility shift assay. Nucleotides important for the observed binding activity will be identified and the insulin-responsive DNA-binding protein characterized. Preliminary data identifies an insulin-induced trans-acting factor which binds to the GH promoter in a sequence specific manner. The functional role of the identified insulin-responsive DNA-binding proteins will be tested by in vitro mutagenesis and transient transfection experiments. Candidate: The P.I. has a sound clinical training and has acquired the necessary molecular techniques to answer fundamental questions as a physician-scientist in an academic environment. The environment: The proposed studies will be performed in the well equipped laboratory of the sponsor from whom the applicant has received excellent training and guidance in the past. The applicant will also be exposed to senior researchers in areas of pituitary gene expression and tumorigenesis, diabetes, bone and vitamin D metabolism, lipids, placental proteins and thyroid tumorigenesis. Significance: This project will provide insight into the mechanisms of nuclear insulin signaling and in the long term will enhance our understanding of insulin regulation of cellular proteins as well as specific gene expression. This will provide fundamental information on the mechanism of insulin action and the pathogenesis of complications found in clinical states of insulin deprivation or attenuated insulin action. This award will afford the applicant an opportunity to develop as an independent clinical investigator.